Expansion valve

Abstract

The expansion valve of the present invention comprises of a heat sensing shaft 36 f equipped to the expansion valve 10 and a diaphragm 36 a contacting its surface, a large stopper portion 312 for receiving the diaphragm 36 a, a large radius portion 314 movably inserted to the lower pressure activate chamber 36 c and contacting the back surface of the stopper portion 312 at one end surface and the center of the other end surface formed at the projection 315, and a rod portion 316 whose one end surface fit to the projection 315 of the large radius portion 314 and the other end surface continuing from the valve means 32 b, wherein a concave 317 is formed on the outer peripheral of said projection 315. This concave 317 is the fitting means for fitting the resin 101 having low heat transmission rate to the heat sensing shaft in order to prevent the occurrence of hunting phenomenon.

What is claimed is:  
     
       1. An expansion valve comprising: 
       a valve body having a first path adapted for passage of a liquid-phase refrigerant to an evaporator and a second path adapted for passage of a gas-phase refrigerant from the evaporator to a compressor;  
       an orifice mounted inside the first path;  
       a valve in the first path, the valve controlling the amount of refrigerant passing through the orifice;  
       a power element portion connected to the valve body and having a diaphragm displaceable in accordance with the temperature of the gas-phase refrigerant;  
       a large radius portion operably connected to the diaphragm;  
       a heat sensing shaft having an upper end abutting the large radius portion and having a lower end abutting the valve so that the valve is controlled by the diaphragm displacement, at least a portion of the heat sensing shaft being adapted to be exposed to the gas-phase refrigerant; and  
       a low heat sensitive member connected to the large radius portion,  
       wherein the low heat sensitive member is made of a material that slowly conducts heat.  
     
     
       2. An expansion valve according to claim  1 , wherein the low heat sensitive member is made of a resin with a low coefficient of heat conductivity. 
     
     
       3. An expansion valve according to claim  2 , wherein the resin is polyacetal. 
     
     
       4. An expansion valve comprising: 
       A valve body having a first path adapted for passage of a liquid-phase refrigerant to an evaporator and a second path adapted for passage of a gas-phase refrigerant from the evaporator to a compressor;  
       an orifice mounted inside the first path;  
       a valve in the first path, the valve controlling the amount of refrigerant passing through the orifice;  
       a power element portion connected to the valve body and having a diaphragm displaceable in accordance with the temperature of the gas-phase refrigerant;  
       a large radius portion operably connected to the diaphragm;  
       a heat sensing shaft having an upper end abutting the large radius portion and having a lower end abutting the valve so that the valve is controlled by the diaphragm displacement, at least a portion of the heat sensing shaft being adapted to be exposed to the gas-phase refrigerant; and  
       a low heat sensitive member connected to the large radius portion;  
       wherein the low heat sensitive member is made of a material that slowly conducts heat;  
       wherein the low heat sensitive member comprises a cylindrical portion and a flange extending substantially radially outwardly at one end thereof, the flange abutting the large radius portion.  
     
     
       5. An expansion valve according to claim  4 , further including a stopper portion having a first surface contacting the diaphragm and a second surface opposite the first surface, wherein the large radius portion has a first surface that contacts the second surface of the stopper portion. 
     
     
       6. An expansion valve according to claim  5 , wherein the large radius portion has a second surface and a substantially cylindrical projection extending outwardly from the second surface thereof, the substantially cylindrical projection forming a hollow cavity, which receives the upper end of the heat sensing shaft, the flange abutting the second surface of the large radius portion. 
     
     
       7. An expansion valve according to claim  6 , wherein the substantially cylindrical portion is inserted into the cylindrical portion of the low heat sensitive member. 
     
     
       8. An expansion valve according to claim  7 , wherein the substantially cylindrical portion has a protrusion extending radially inwardly from an inner periphery thereof, and an outer periphery of the substantially cylindrical projection has a groove that receives the protrusion to secure the low heat sensitive member to the large radius portion. 
     
     
       9. An expansion valve comprising: 
       A valve body having a first path adapted for passage of a liquid-phase refrigerant to an evaporator and a second path adapted for passage of a gas-phase refrigerant from the evaporator to a compressor;  
       an orifice mounted inside the first path;  
       a valve in the first path, the valve controlling the amount of refrigerant passing through the orifice;  
       a power element portion connected to the valve body and having a diaphragm displaceable in accordance with the temperature of the gas-phase refrigerant;  
       a large radius portion operably connected to the diaphragm;  
       a heat sensing shaft having an upper end abutting the large radius portion and having a lower end abutting the valve so that the valve is controlled by the diaphragm displacement, at least a portion of the heat sensing shaft being adapted to be exposed to the gas-phase refrigerant; and  
       a low heat sensitive member connected to the large radius portion;  
       wherein the low heat sensitive member is made of a material that slowly conducts heat;  
       wherein the valve body has an opening for passage of the heat sensing shaft, the opening extending between the first path and the second path, and further including a sealing ring mounted on the heat sensing shaft, the sealing ring preventing the refrigerant leaking through the opening, and a preventing member that prevents the sealing ring from being displaced.  
     
     
       10. An expansion valve according to claim  9 , wherein the preventing member is a self-locking nut. 
     
     
       11. An expansion valve according to claim  10 , wherein the self-locking nut is a push nut. 
     
     
       12. An expansion valve according to claim  9 , wherein the preventing member is a first snap ring, the heat sensing shaft having a first groove for receiving the snap ring. 
     
     
       13. An expansion valve according to claim  12 , wherein the first snap ring has a plurality of inner teeth engaging the groove. 
     
     
       14. An expansion valve according to claim  13 , further including a second snap ring, the heat sensing shaft having a second groove spaced axially from the first groove, the first and second snap rings sandwiching the sealing ring to immobilize the sealing ring.